1. Field of the invention
This invention relates to an electric power generating element capable of efficiently converting a low-temperature heat energy to an electric energy.
2. Description of the Prior Art
Demands for diversification of energy resources, global environment protection and so on have proposed applications of thermoelectric generation of electricity employing a thermoelectric generating element by use of the Seebeck effect to a small-scale power generation. For example, a fossil fuel such as propane is burned by means of a burner and then, a heat source with a capacity up to 820 K. obtained from the burning of the fossil fuel is applied to a thermoelectric generating element composed of the system of PbTe so that thermo-electromotive force is generated by the Seebeck effect. In another proposed method, the fossil fuel is gradually burned in the presence of a platinum catalyst such that a heat source with a capacity up to 600 K. is obtained. The heat source is applied to a thermoelectric generating element composed of the system of BiTe. In further another proposed method, a nuclear reactor or radioactive elements are used as the heat source to apply heat to a thermoelectric generating element composed of the system of SiGe when the supply of the fossil fuel is difficult.
However, a high-temperature heat source is required in the above-described conventional methods of the thermoelectric generation of electricity, resulting in a low efficiency of thermoelectric conversion. Further, the fossil fuel, the nuclear reactor or the radioactive element is required to obtain the high-temperature heat source and accordingly, a large-scale apparatus for the thermoelectric generation is necessitated. Thus, the conventionally proposed methods of thermoelectric generation are contrary to demands for compactness and cost effectiveness. Further, the running cost would become high and a sufficient energy saving effect would not be expected.
The prior art also provides as another related art a solar battery wherein solar energy is converted to electric energy by the photovoltaic effect. The solar battery is expensive and cannot be used when the sunlight is not available. Further, the solar battery has a critical defect that the heat energy other than light energy cannot be converted to the electric energy. Additionally, the solar battery requires a large space for receiving the sunlight, which is contrary to the demands for compactness and cost effectiveness.